impact of modern agriculture on environment

Best Results From
Wikipedia Yahoo Answers Encyclopedia

From Wikipedia

Agriculture and the environment

Agricultureand theenvironmentare intimately linked and much debate has taken place in recent years about thesustainability of some farming practices. Farming efficiencies, technological innovations and organic farming are all used to reduce the environmental impact of farming.

Effects

Agricultural chemicals

Climate change

Fertilizers

Fertilizers are often used to replenish the loss of nutrients due to farming. Overuse of fertilizers can result in nutrient runoff polluting nearby water bodies and is a cause of eutrophication. An innovative approach to best management practices (BMPs) for fertilizer is the Right Source, Right Rate, Right Time, Right Place concept. It is also known as 4R nutrient stewardship. It can be applied to managing either crop nutrients in general (including organic sources) or fertilizers in specific. This concept can help farmers and the public understand how the right management practices for fertilizer contribute to sustainability goals for agriculture. In a nutshell, the 4R nutrient stewardship concept involves crop producers and their advisers selecting the right source-rate-time-place combination from practices validated by research conducted by agronomic scientists. Goals for economic, environmental and social progress are set byâ€”and are reflected in performance indicators chosen byâ€”the stakeholders to crop production systems.

Agriculture and agricultural science

The two terms are often confused. However, they cover different concepts:

Agriculture is the set of activities that transform the environment for the production of animals and plants for human use. Agriculture concerns techniques, including the application of agronomic research.

Agricultural science: a local science

With the exception of theoretical agronomy, research in agronomy, more than in any other field, is strongly related to local areas. It can be considered a science of ecoregions, because it is closely linked to soil properties and climate, which are never exactly the same from one place to another. Many people think an agricultural production system relying on local weather, soil characteristics, and specific crops has to be studied locally. Others feel a need to know and understand production systems in as many areas as possible, and the human dimension of interaction with nature.

History of agricultural science

Agricultural science began with Gregor Mendel's genetic work, but in modern terms might be better dated from the chemical fertilizer outputs of plant physiological understanding in eighteenth century Germany. In the United States, a scientific revolution in agriculture began with the Hatch Act of 1887, which used the term "agricultural science". The Hatch Act was driven by farmers' interest in knowing the constituents of early artificial fertilizer. The Smith-Hughes Act of 1917 shifted agricultural education back to its vocational roots, but the scientific foundation had been built. After 1906, public expenditures on agricultural research in the US exceeded private expenditures for the next 44 years.

As the oldest and largest human intervention in nature, the environmental impact of agriculture in general and more recently intensive agriculture, industrial development, and population growth have raised many questions among agricultural scientists and have led to the development and emergence of new fields. These include technological fields that assume the solution to technological problems lies in better technology, such as integrated pest management, waste treatment technologies, landscape architecture, genomics, and agricultural philosophy fields that include references to food production as something essentially different from non-essential economic 'goods'. In fact, the interaction between these two approaches provide a fertile field for deeper understanding in agricultural science.

Prominent agricultural scientists

biodiversity. It includes all forms of life directly relevant to agriculture: rare seed varieties and animal breeds (farm biodiversity), but also many other organisms such as soil fauna, weeds, pests, predators, and all of the native plants and animals (wild biodiversity) existing on and flowing through the farm. However, most attention in this field is given to crop varieties and to crop wild relatives. Cultivated varieties can be broadly classified into â€œmodern varietiesâ€� and â€œfarmerâ€™s or traditional varietiesâ€�. Modern varieties are the outcome of formal breeding and are often characterized as 'high yielding'. For example the short straw wheat and rice varieties of the Green Revolution. In contrast, farmerâ€™s varieties (also known as landraces) are the product of (breeding and) selection carried out by farmers. Together, these varieties represent high levels of genetic diversity and are therefore the focus of most crop genetic resources conservation efforts. Agricultural biodiversity is the basis of our agricultural food chain, developed and safeguarded by farmers, livestock breeders, forest workers, fishermen and indigenous peoples throughout the world. The use of agricultural biodiversity (as opposed to non diverse production methods) can contribute to food security and livelihood security.

Scope

Although the term agricultural biodiversity is relatively new - it has come into wide use in recent years as evidenced by bibliographic references - the concept itself is quite old. It is the result of the careful selection and inventive developments of farmers, herders and fishers over millennia. Agricultural biodiversity is a vital sub-set of biodiversity. It is a use of life, i.e. ancillary biotechnologies, by Mankind whose food and livelihood security depend on the sustained management of those diverse biological resources that are important for food and agriculture.. As for everything, agricultural biodiversity can be used, not used, misused and even abused. Agricultural biodiversity includes:

Non-harvested species within production agroecosystems that support food provision, including soil micro-biota, pollinators and so on

Non-harvested species in the wider environment that support food production agroecosystems (agricultural, pastoral, forest and aquatic ecosystems)

However, agricultural biodiversity, sometimes called Agrobiodiversity, "encompasses the variety and variability of animals, plants andmicro-organisms which are necessary to sustain key functions of the agroecosystem, its structure and processes for, and in support of, food production and food security".. It further "comprises genetic, population, species, community, ecosystem, and landscape components and human interactions with all these."

Aquatic diversity is also an important component of agricultural biodiversity. The conservation and sustainable use of local aquatic ecosystems, ponds, rivers, coastal commons by artisanal fisherfolk and smallholder farmers is important to the survival of both humans and the environment. Since aquatic organisms, including fish, provide much of our food supply as well as underpinning the income of coastal peoples, it is critical that fisherfolk and smallholder farmers have genetic reserves and sustainable ecosystems to draw upon as aquaculture and marine fisheries management continue to evolve.

Genetic erosion in Agricultural and livestock biodiversity

Genetic erosion in Agricultural and livestock biodiversity is the loss of genetic diversity, including the loss of individual genes, and the loss of particular combinants of genes (or gene complexes) such as those manifested in locally adapted landraces. The term genetic erosion is sometimes used in a narrow sense, such as for the loss of alleles or genes, as well as more broadly, referring to the loss of varieties or even species. The major driving forces behind genetic erosion in crops are: variety replacement, land clearing, overexploitation of species, population pressure, environmental degradation, overgrazing, policy and changing agricultural systems.

The main factor, however, is the replacement of local varieties by high yielding or exotic varieties or species. A large number of varieties can also often be dramatically reduced when commercial varieties (including GMOs) are introduced into traditional farming systems. Many researchers believe that the main problem related to agro-ecosystem management is the general tendency towards genetic and ecological uniformity imposed by the development of modern agriculture. Pressures for that ecological uniformity on farmers and breeders is caused by the food industry demand for more and more raw materials consistency.

Human dependency

Agricultural biodiversity is not only the result of human activity but human life is dependent on it not just for the immediate provision of food and other natural resources based goods, but for the maintenance of areas of land and waters that will sustain production and maintain agroecosystems and the wider biological and environmental services (biosphere).

Agricultural Biodiversity provides:

Sustainable production of food and other agricultural products emphasising both strengthening sustainability in production systems at all levels of intensity and improving the conservation, sustainable use and enhancement of the diversity of all genetic resources for food and agricul

From Encyclopedia

Agriculture, Modern

During the latter half of the twentieth century, what is known today as modern agriculture was very successful in meeting a growing demand for food by the world's population. Yields of primary crops such as rice and wheat increased dramatically, the price of food declined, the rate of increase in crop yields generally kept pace with population growth, and the number of people who consistently go hungry was slightly reduced. This boost in food production has been due mainly to scientific advances and new technologies, including the development of new crop varieties, the use of pesticides and fertilizers, and the construction of large irrigation systems. Modern agricultural systems have been developed with two related goals in mind: to obtain the highest yields possible and to get the highest economic profit possible. In pursuit of these goals, six basic practices have come to form the backbone of production: intensive tillage, monoculture , application of inorganic fertilizer, irrigation, chemical pest control, and genetic manipulation of crop plants. Each practice is used for its individual contribution to productivity, but when they are all combined in a farming system each depends on the others and reinforces the need for using the others. The work of agronomists, specialists in agricultural production, has been key to the development of these practices. The soil is cultivated deeply, completely, and regularly in most modern agricultural systems, and a vast array of tractors and farm implements have been developed to facilitate this practice. The soil is loosened, water drains better, roots grow faster, and seeds can be planted more easily. Cultivation is also used to control weeds and work dead plant matter into the soil. When one crop is grown alone in a field, it is called a monoculture. Monoculture makes it easier to cultivate, sow seed, control weeds, and harvest, as well as expand the size of the farm operation and improve aspects of profitability and cost. At the same time, monocultures tend to promote the use of the other five basic practices of modern agriculture. Very dramatic yield increases occur with the application of synthetic chemical fertilizers. Relatively easy to manufacture or mine, to transport, and to apply, fertilizer use has increased from five to ten times what it was at the end of World War II (1939-45). Applied in either liquid or granular form, fertilizer can supply crops with readily available and uniform amounts of several essential plant nutrients. By supplying water to crops during times of dry weather or in places of the world where natural rainfall is not sufficient for growing most crops, irrigation has greatly boosted the food supply. Drawing water from underground wells, building reservoirs and distribution canals, and diverting rivers have improved yields and increased the area of available farm land. Special sprinklers, pumps, and drip systems have greatly improved the efficiency of water application as well. In the large monoculture fields of much of modern agriculture, pests include such organisms as insects that eat plants, weeds that interfere with crop growth, and diseases that slow plant and animal development or even cause death. When used properly, synthetic chemicals have provided an effective, relatively easy way to provide such control. Chemical sprays can quickly respond to pest outbreaks. Farmers have been choosing among crop plants and animals for specific characteristics for thousands of years. But modern agriculture has taken advantage of several more recent crop breeding techniques. The development of hybrid seed, where two or more strains of a crop are combined to produce a more productive offspring, has been one of the most significant strategies. Genetic engineering has begun to develop molecular techniques that selectively introduce genetic information from one organism to another, often times from very unrelated organisms, with a goal of capitalizing on specific useful traits. But for almost every benefit of modern agriculture, there are usually problems. Excessive tillage led to soil degradation, the loss of organic matter, soil erosion by water and wind, and soil compaction . Large monocultures are especially prone to devastating pest outbreaks that often occur when pests encounter a large, uniform area of one crop species, requiring the continued and excessive use of chemical sprays. When used excessively, chemical fertilizers can be easily leached out of the soil into nearby streams and lakes, or even down into underground water supplies. Farmers can become dependent on chemical pest and weed control. Modern farm systems lack the natural control agents needed for biological pest management, and larger amounts of sprays must be used as pests rapidly evolve resistance. People also worry about chemical pollution of the environment by sprays and fertilizers, and the possible contamination of food supplies. Modern agriculture has become such a large user of water resources that overuse, depletion, saltwater contamination, salt buildup in soil, fertilizer leaching, and soil erosion have become all too common. Agricultural water users compete with urban and industrial use, and wildlife as well. Hybrid seed has contributed greatly to the loss of genetic diversity and increased risk of massive crop failure, as well as an increased dependence on synthetic and non-renewable inputs needed for maintaining high yield. Genetically engineered crops have the same negative potential, especially as the selection process takes place less and less in the hands of farmers working in their own fields, but rather in far away laboratories. In the future, in order to take advantage of new technologies and practices, farming systems will need to be viewed as ecosystems , or agricultural ecosystems. By monitoring both the positive and negative impacts of modern farming practices, ecologically based alternatives can be developed that protect the health of the soil, air, and water on farms and nearby areas, lower the economic costs of production, and promote viable farming communities around the world. Organic agriculture, conservation tillage, integrated pest management (IPM), and the use of appropriate genetic techniques that enhance local adaptation and variety performance are a few of the possible ways of ensuring the sustainability of future generations of farmers. see also Agricultural Ecosystems; Agriculture, History of; Agriculture, Organic; Agronomist; Breeder; Breeding; Fertilizer; Herbicides. Stephen R. Gliessman Brown, Lester R. "Struggling to Raise Cropland Productivity." In State of the World: 1998, eds. Lester Brown, Christopher Flavin, and Hilary French. New York: W.W. Norton and Company, 1998. Gliessman, Stephen R. Agroecology: Ecological Processes in Sustainable Agriculture. Chelsea, MI: Ann Arbor Press, 1998.

Environment Environment

The term "environment" means the surroundings of a living creature. It can also refer to all the factors of the external world that affect biological and social activities. There are abiotic (nonliving) environmental factors such as sunlight, air, and water. There are also biotic (living or recently living) environmental factors such as plants, animal predators, and food. The total environment of an organism is the sum total of the biotic and abiotic environments. The study of the relationships between living creatures and their environments is called ecology. A human's abiotic environment includes things such as weather (sun-light, wind, air temperature) and items which give protection from the weather (clothes or houses). Other abiotic factors are the soil and water, and chemicals in the soil and water. A human's biotic environment includes things such as food (plants and animals), other humans, animals, trees, and grasses. The biotic environment also includes how living creatures interact with each other and their abiotic environments. Therefore, a human's biotic environment also consists of social or cultural surroundings. Humans learn from each other how to behave in socially acceptable ways. They also pass along knowledge about language, science, and art. The major components of Earth's physical environment are the atmosphere, climate and weather, land, and bodies of water such as lakes, rivers, and oceans. The term "environment" is commonly associated with the impact that humans have made on the natural world. Increasing human population and industrial activities have led to problems associated with the pollution of air, water, and soil. Pollution has a negative impact on humans in terms of health and quality of life, as well as on other animals and plants. Human activities such as the dumping of industrial wastewater and poorly treated sewage water have led to the pollution of fresh and salt water. Groundwater, water beneath the land surface that often serves as drinking water for humans, has also been negatively affected. Accidental oil spills from ships and untreated storm-water runoff from urban and agricultural areas also degrade bodies of water. Air pollution results from human activities such as burning fossil fuels (oil, coal, and gasoline) to create electricity and power automobiles, and manufacturing industrial products such as chemicals and plastic. Burning fossil fuels releases carbon dioxide into the atmosphere, adding billions of extra tons of carbon to the natural carbon cycle. Deforestation and poor soil management also add carbon. Most scientists believe that the increased carbon dioxide in the atmosphere contributes to the potentially devastating warming of the global climate, the so-called "greenhouse effect." Another human impact on the atmosphere has been depletion of the ozone layer. The ozone layer helps filter ultraviolet light and protects Earth's surface from harmful doses of radiation. Many scientists believe that chlorofluoro-carbons used as coolants in air conditioners and refrigeration units destroy ozone when released into the atmosphere. Land pollution is caused by poor agricultural practices, mining for coal and minerals, and dumping industrial and urban wastes. The widespread usage of pesticides has led to pollution of both soils and bodies of water. As more and more environmental problems become evident, humans will have to assess their activities and their impact on the natural world. see also Biome; Ecosystem; Habitat. Denise Prendergast

Sustainable Agriculture

Thanks to a complex international system of production, processing, shipping, and marketing, people today can eat a vast selection of out-of-season and out-of-region fruits and vegetables year round. In addition, modern farming practices have provided an abundant, not just a varied, food supply. However, the availability of abundant and varied food relies on energy-intensive, nonrenewable resources such as fossil fuels, and many practices associated with agribusiness have had a detrimental impact on the environment. Agribusiness looks at farms as factories to be run as profitably and efficiently as possible. "How much, how fast" replaces the old values of carrying capacity (how much the land can yield without being depleted) and a season of lying fallow. Monocropping (fields used for only one crop, the same crop year after year, commonly wheat, soybeans or cotton) and increased field size do away with biodiversity and hedgerows, and thus with fertility, pollinators, and resistance to insects and disease. Millions of tons of chemical fertilizers applied to fields destroy microorganisms that are vital to the health of the soil. The intensive use of herbicides and pesticides kills pollinating insects that are essential for crop production. Manure and crop residues, once valuable sources of soil nutrition, are no longer tilled in and have become polluting waste products themselves, to be burned or dumped. Underground aquifers (natural water reservoirs) that took thousands of years to fill are pumped dry to irrigate fields in semi-arid regions. Additionally, ground water is full of dissolved mineral salts. As the water evaporates it leaves a salt concentration buildup that is poisoning the soil. Intensive plowing opens up hundreds of thousands of acres of topsoil to erosion by wind and rain, filling the air with dust or silting up waterways. As more and more wild land is converted to growing one particular crop on a massive scale, genetic biodiversity diminishes. Rain forests are bulldozed to provide pastures for cheap beef. Massive feedlot operations are susceptible to catastrophic diseases, and they pollute drinking water supplies with their tons of confined manure. Agribusiness also affects the economy. Family farmers are increasingly replaced by corporate managers, and the price of farm equipment and capital outlay soars. Profits from production may go to a large company based far away from the actual farm and never enter the local economy. In addition, large-scale food production and distribution have become vulnerable to the vagaries of international politics and the stock market, and any breakdown in the network places everyone at risk. The price of oil, interest rates, trucking fees, politics and the weather all affect the availability and price of food. In countries where there is economic or military chaos, even though there might be plenty of food on farms or at food aid centers, the breakdown in the complex distribution system results in famine. Sustainable agriculture is the practice of working in concert with nature to replenish the soil in order to assure a secure, affordable food supply without depleting natural resources or disrupting the cycles of life. Proponents of sustainable agriculture suggest we can reverse the damage done by agribusiness. They believe that a dependable long-term food supply must rely on the protection of resourcesâ€”seeds, food species, soil, breeding stock, and the water supply, as well as the farmer who knows and cares for a particular piece of land and the community with which the farmer is interdependent. Sustainable agriculture promotes regional and local small-scale farms that rely on the interplay of crops and livestock to replenish the soil and control erosion. The aim of a healthy farm is to produce as many kinds of plants and animals as it reasonably can. Ordered diversity is the practice of maintaining many kinds of plants and animals together to complement one another. The practice of planting a noncommercial crop on fields to increase fertility, conserve soil moisture, keep topsoil from eroding or blowing away and encourage soil microrganisms is called cover cropping. Soil fertility, which is the major capital of any farm, can be largely maintained within the farm itself by this method and by plowing back in manure and other organic wastes. Food grown for local consumption is more fresh, can be harvested when ripe, and uses less energy to get to market. Farm stands and local farmers' markets provide more money for the farmer and higher quality, lower-price food for the consumer. Sustainable agriculture embraces diversity of method and scale, looking for what is appropriate to a given location. One example is urban homesteading, in which thousands of vacant inner-city lots can be used to grow neighborhood gardens. Renewable energy sources, such as passive-solar greenhouses or windmills, are encouraged. Sustainable agriculture advocates organic solutions to pest control such as crop rotation, the introduction and maintenance of beneficial insects, and intercropping (growing more than one kind of crop on the same land in the same growing season). All these methods discourage insect infestations, thus reducing the amount of pesticides in the environment. Agriculture cannot survive for long at the expense of the natural systems that support it. And a culture cannot survive at the expense of its agriculture. see also Farming. Nancy Weaver Berry, Wendell. The Unsettling of America: Culture and Agriculture. San Francisco: Sierra Club Books, 1977. Organic Farming Research Foundation. Winter 2001 Information Bulletin, no. 9. Erica Walz, ed. Santa Cruz, CA: Organic Farming Research Foundation, 2001.

Agricultural Biotechnology

Biotechnology is the use of living organismsâ€”microbes, plants, or animalsâ€”to provide useful new products or processes. In a broad sense, biotechnology continues a process that is thousands of years old. Using traditional plant breeding techniques, humans have altered the genetic composition of almost every crop by only planting seeds from plants with desired traits, or by controlling pollination. As a result, most commercial crops bear little resemblance to their early relatives. Current maize varieties are so changed from their wild progenitors that they cannot survive without continual human intervention. The 1970s heralded recombinant DNA technology, which gave researchers the ability to cut and recombine DNA fragments from different sources to express new traits. Genes and traits previously unavailable through traditional breeding became available through DNA recombination. Modern plant genetic engineering involves transferring desired genes into the DNA of some plant cells and regenerating a whole plant from the transformed tissue. New DNA may be introduced into the cell via biological or physical means. The most widely used biological method for transferring genes into plants capitalizes on a trait of a naturally occurring soil bacterium, Agrobacterium tumefaciens, which causes crown gall disease. This bacterium, in the course of its natural interaction with plants, has the ability to infect a plant cell and transfer a portion of its DNA into a plant's genome . This leads to an abnormal growth on the plant called a gall. Scientists take advantage of this natural transfer mechanism by first removing the disease-causing genes and then inserting a new beneficial gene into A. tumefaciens. The bacteria then transfer the new gene into the plant. Another gene transfer technique involves using a "gene gun" to literally shoot DNA through plant cell walls and membranes to the cell nucleus, where the DNA can combine with the plant's own genome. In this technique, the DNA is made to adhere to microscopic gold or tungsten particles and is then propelled by a blast of pressurized helium. Depending on which genes are transferred, agricultural biotechnology can protect crops from disease, increase their yield, improve their nutritional content, or reduce pesticide use. In 2000, more than half of American soybeans and cotton and one-fourth of American corn crops were genetically modified by modern biotechnology techniques. Genetically modified foods may also help people in developing countries. One in five people in the developing world do not have access to enough food to meet their basic nutritional needs. By enhancing the nutritional value of foods, biotechnology can help improve the quality of basic diets. "Golden rice" is a form of rice engineered to contain increased amounts of vitamin A. Researchers are also developing rice and corn varieties with enriched protein contents, as well as soybean and canola oils with reduced saturated fat. Other potential benefits include crops that can withstand drought conditions or high salinity, allowing populations living in harsh regions to farm their land. Agricultural biotechnology also provides benefits for the manufacture of pharmaceutical products. Because plants do not carry human diseases, plant-made vaccines and antibodies require less screening for bacterial toxins and viruses. In addition to plants, animals may also be engineered to produce beneficial genes. In order to produce large quantities of monoclonal antibodies for research on new therapeutic drugs, several companies have genetically engineered cows and goats to secrete antibodies into their milk. One company has inserted a spider gene into dairy goats. The spider silk extracted from the goat's milk is expected to produce fibers for bulletproof vests and medical supplies, such as stitch thread, and other applications where flexible and extremely strong fibers are required. Despite the benefits of genetic engineering, there are concerns about whether recombinant DNA techniques carry greater risks than traditional breeding methods. Consumer acceptance of food derived from genetically engineered crops has been variable. Many individuals express concerns regarding the environmental impact and ethics of the new technology, and about food safety. One of the major food safety concerns is that there is a risk that crops expressing newly inserted genes may also contain new allergens . Some groups have expressed concern that widespread use of plants engineered for specific types of pest resistance could accelerate the development of pesticide-resistant insects or have negative effects on organisms that are not crop pests. Another environmental concern is that transgenic, pest-protected plants could hybridize with neighboring wild relatives, creating "superweeds" or reducing genetic biodiversity . To address these concerns, agricultural biotechnology products are regulated by a combination of three federal agencies: the U.S. Department of Agriculture (USDA), the Environmental Protection Agency (EPA), and the Food and Drug Administration (FDA). Together, these agencies assess genetically modified crops, as well as products that use those crops. They test the crops and products for safety to humans and to the environment, and for their efficacy and quality. see also Biopesticides; Genetically Modified Foods; Plant Genetic Engineer; Transgenic Animals; Transgenic Microorganisms; Transgenic Plants. Barbara Emberson Soots Ferber, Dan. "Risks and Benefits: GM Crops in the Cross Hairs." Science 286 (1999): 1662-1666. Agricultural Biotechnology. U.S. Department of Agriculture. . Transgenic Plants and World Agriculture. Royal Society of London, U.S. National Academy of Sciences, Brazilian Academy of Sciences, Chinese Academy of Sciences, Indian National Science Academy, Mexican Academy of Sciences, and Third World Academy of Sciences. .

From Yahoo Answers

Question:Problems such as the need to preserve traditional methods and knowledge to prevent drought,famine and reduce malnutrition.

Answers:Until about four decades ago, crop yields in agricultural systems depended on internal resources, recycling of organic matter, built-in biological control mechanisms and rainfall patterns. Agricultural yields were modest, but stable. Production was safeguarded by growing more than one crop or variety in space and time in a field as insurance against pest outbreaks or severe weather. Inputs of nitrogen were gained by rotating major field crops with legumes. In turn rotations suppressed insects, weeds and diseases by effectively breaking the life cycles of these pests. A typical corn belt farmer grew corn rotated with several crops including soybeans, and small grain production was intrinsic to maintain livestock. Most of the labor was done by the family with occasional hired help and no specialized equipment or services were purchased from off-farm sources. In these type of farming systems the link between agriculture and ecology was quite strong and signs of environmental degradation were seldom evident (1) .
But as agricultural modernization progressed, the ecology-farming linkage was often broken as ecological principles were ignored and/or overridden. In fact, several agricultural scientists have arrived at a general consensus that modern agriculture confronts an environmental crisis. A growing number of people have become concerned about the long-term sustainability of existing food production systems. Evidence has accumulated showing that whereas the present capital- and technology-intensive farming systems have been extremely productive and competitive, they also bring a variety of economic, environmental and social problems (2) .
Evidence also shows that the very nature of the agricultural structure and prevailing policies have led to this environmental crisis by favoring large farm size, specialized production, crop monocultures and mechanization. Today as more and more farmers are integrated into international economies, imperatives to diversity disappear and monocultures are rewarded by economies of scale. In turn, lack of rotations and diversification take away key self-regulating mechanisms, turning monocultures into highly vulnerable agroecosystems dependent on high chemical inputs.
The expansion of monocultures
Today monocultures have increased dramatically worldwide, mainly through the geographical expansion of land devoted to single crops and year-to-year production of the same crop species on the same land. Available data indicate that the amount of crop diversity per unit of arable land has decreased and that croplands have shown a tendency toward concentration. There are political and economic forces influencing the trend to devote large areas to monoculture, and in fact such systems are rewarded by economies of scale and contribute significantly to the ability of national agricultures to serve international markets.
The technologies allowing the shift toward monoculture were mechanization, the improvement of crop varieties, and the development of agrochemicals to fertilize crops and control weeds and pests. Government commodity policies these past several decades encouraged the acceptance and utilization of these technologies. As a result, farms today are fewer, larger, more specialized and more capital intensive. At the regional level, increases in monoculture farming meant that the whole agricultural support infrastructure (i.e. research, extension, suppliers, storage, transport, markets, etc.) has become more specialized.
From an ecological perspective, the regional consequences of monoculture specialization are many-fold:
Most large-scale agricultural systems exhibit a poorly structured assemblage of farm components, with almost no linkages or complementary relationships between crop enterprises and among soils, crops and animals.
Cycles of nutrients, energy, water and wastes have become more open, rather than closed as in a natural ecosystem. Despite the substantial amount of crop residues and manure produced in farms, it is becoming increasingly difficult to recycle nutrients, even within agricultural systems. Animal wastes cannot economically be returned to the land in a nutrient-recycling process because production systems are geographically remote from other systems which would complete the cycle. In many areas, agricultural waste has become a liability rather than a resource. Recycling of nutrients from urban centers back to the fields is similarly difficult.
Part of the instability and susceptibility to pests of agroecosystems can be linked to the adoption of vast crop monocultures, which have concentrated resources for specialist crop herbivores and have increased the areas available for immigration of pests. This simplification has also reduced environmental opportunities for natural enemies. Consequently, pest outbreaks often occur when large numbers of immigrant pests, inhibited populations of beneficial insects, favorable weather and vulnerable crop stages happen simultaneously.
As specific crops are expanded beyond their "natural" ranges or favorable regions to areas of high pest potential, or with limited water, or low-fertility soils, intensified chemical controls are required to overcome such limiting factors. The assumption is that the human intervention and level of energy inputs that allow these expansions can be sustained indefinitely.
Commercial farmers witness a constant parade of new crop varieties as varietal replacement due to biotic stresses and market changes has accelerated to unprecedented levels. A cultivar with improved disease or insect resistance makes a debut, performs well for a few years (typically 5-9 years) and is then succeeded by another variety when yields begin to slip, productivity is threatened, or a more promising cultivar becomes available. A variety s trajectory is characterized by a take-off phase when it is adopted by farmers, a middle stage when the planted area stabilizes and finally a retraction of its acreage. Thus, stability in modern agriculture hinges on a continuous supply of new cultivars rather than a patchwork quilt of many different varieties planted on the same farm.
The need to subsidize monocultures requires increases in the use of pesticides and fertilizers, but the efficiency of use of applied inputs is decreasing and crop yields in most key crops are leveling off. In some places, yields are actually in decline. There are different opinions as to the underlying causes of this phenomenon. Some believe that yields are leveling off because the maximum yield potential of current varieties is being approached, and therefore genetic engineering must be applied to the task of redesigning crop. Agroecologists, on the other hand, believe that the leveling off is because of the steady erosion of the productive base of agriculture through unsustainable practices (3).
The first wave of environmental problems
The specialization of production units has led to the image that agriculture is a modern miracle of food production. Evidence indicates, however, that excessive reliance on monoculture farming and agroindustrial inputs, such as capital-intensive technology, pesticides, and chemical fertilizers, has negatively impacted the environment and rural society. Most agriculturalists had assumed that the agroecosystem/natural ecosystem dichotomy need not lead to undesirable consequences, yet, unfortunately, a number of "ecological diseases" have been associated with the intensification of food production. They may be grouped into two categories: diseases of the ecotope, which include erosion, loss of soil fertility, depletion of nutrient reserves, salinization and alkalinization, pollution of water systems, loss of fertile croplands to urban development, and diseases of the biocoenosis, which include loss of crop, wild plant, and animal genetic resources, elimination of natural enemies, pest resurgence and genetic resistance to pesticides, chemical contamination, and destruction of natural control mechanisms. Under conditions of intensive management, treatment of such "diseases" requires an increase in the external costs to th

Question:more specifically looking at era between 18th - 20th century. How did the imperialists impact the native agricultre and forestry?
what was the deforestation impact?
What were the positive & negative impacts of imperialism and colonialism on the environment?

Question:Please someone help me fast i left my book in class.. Help!!
1. Describe chlorinated hydrocarbons are an environmental threat even though their use has been banned in the U.S.
2. Why supplies of soil and ground water are dwindling even though these resources are replenished by natural processes?
3. Describe two instances in which technology has caused the growth rate of the human population yo increase.
4. A class-mate claims that the growth rate of the human population will not affect populations of other species . do u agree or not?
5.Describe two harmful effects of acid rain.
6.How will the delpetion of the ozone layer affect human healths?
7.Describe the Greenouse effect and its affect on the Earths climate.
8. Some of the pollution from power plants in the U.S. causes acid rain in Canada. So the U.S. pay Canada for its damage to it ecosystem?
9.Describe how fax can reduce pollution.
10. At which step to the solution of an environmantal problem could you have the greatest influence?
11. Of the 5 steps of soling encironmental problems, explain which step you think might be the most difficlut to important.

Answers:1. DDT = chlorinated hydrocarbon. "When DDT enters a water environment, it is taken up by aquatic animals and becomes part of the food chain, accumulating and concentrating in the fat of predatory species. DDT also remains residual in upper soil layers and accumulates in many terrestrial animal species." -http://www.michigan.gov/dnr/0,1607,7-153-10370_12150_12220-26633--,00.html
2. ?
3. Antibiotics, more people survive to reproductive age. agriculture, more people able to be fed.
4. your opinion
5. http://www.epa.gov/acidrain/effects/index.html
6. UV exposure increased, skin cancer increased
7. http://www.epa.gov/climatechange/kids/greenhouse.html
8. hell yes the US should pay up!
9. fax? still uses paper on both ends...so only reduces carbon output from mailing (gas used by mailtruck, paper from envelope)
10. only using energy when necessary, carpooling, not wasting paper...etc.
11. call a classmate, need to know what steps this is referring to

Question:SCIENCE QUESTION: describe agriculture and how it impacts the environment?

Answers:Agriculture has a lot of effects, especially on the soil itself.
Trees are removed to create fields. That is the first problem. The trees and plants are there to help hold the soil together. Once the cover is gone, erosion will start, due to wind/rain etc.
A crop is planted. One singular crop will lead to nutrient deficient soil. They need to be rotated to ensure that the minerals stay in the ground.
Cows/sheep compact the ground due to their hooves, which increases the runoff of water, leading to more erosion. Sheep also eat plants to the ground, killing them and leaving the ground prone to more wind/water erosion.
Lots of water is needed for irrigation. In Australia we're in drought at the moment, so it is very tough to keep things going. Crops die and animals have to eat something - natives, or they are sold and the land stays fallow. More erosion.
Agriculture also uses lots of fertalisers. These may cause problems if they enter a water supply (algal blooms, etc.), and this has its own problems - kills fish, ultimately.
The rate of agriculture will only continue to increase as the population of the earth does, because we will need to feed more and more people!